Originally Posted by
WineCountryUA
This has been an issue with other airlines, such as LH group. There will not / cannot touch a codeshare flight if it involves a financial transaction or a change (such as fare class).
It is interesting UA can do this (E+ fees, upgrades, ...) when they are the flight operator of a codeshare but the above has been reported by many for multiple airlines. A definitive downside for codeshares as more and more airlines are charging for seat assignments.
Thankfully, LH itself has remedied that situation; I had no issue on my two LH flights (CPT-FRA & FRA-LHR) paying $46 (total) for seat assignments. As in the past, my wife's award ticked included free seat assignments. Booking class was S.
In my opinion United should be more proactive in letting people know seat assignments will not be available until T-24 on relevant codeshares.